When three Chinese scientists plunged to the bottom of the South China Sea in a tiny submarine early this summer, they did more than simply plant their nation's flag on the dark seabed.
The men, who descended more than 2 miles in a craft the size of a small truck, also signaled Beijing's intention to take the lead in exploring remote and inaccessible parts of the ocean floor, which are rich in oil, minerals and other resources that the Chinese would like to mine. And many of those resources happen to lie in areas where China has clashed repeatedly with its neighbors over territorial claims.
After the flag planting, which was done in secret but recorded in a video, Beijing quickly turned the feat of technology into a show of bravado.
"It is a great achievement," Liu Feng, director of the dives, was quoted as saying by China Daily, an English-language newspaper, which telegraphs government positions to the outside world.
The global seabed is littered with what experts say is trillions of dollars' worth of mineral nodules as well as many objects of intelligence value: undersea cables carrying diplomatic communications, lost nuclear arms, sunken submarines and hundreds of warheads left over from missile tests.
While a single small craft cannot reel in all these treasures, it does put China in an excellent position to go after them.
"They're in it for a penny and a pound," said Don Walsh, a pioneer of deep-ocean diving who recently visited the submersible and its makers in China. "It's a very deliberate program."
The small craft that made the trip — named Jiaolong, after a mythical sea dragon — was unveiled publicly late last month after eight years of secretive development. It is designed to go deeper than any other in the world, giving China access to 99.8 percent of the ocean floor.
Technically, the Jiaolong is a submersible. These undersea craft differ from submarines in their small size, their need for a mother ship on the surface, and their ability to dive extraordinarily far under the waves despite the inky darkness and the crushing pressures. The world has only a few.
Jiaolong is meant to go as deep as 4.35 miles, edging out the current global leader. Japan's Shinkai 6500 can go about 4 miles, outperforming craft "all over the world," according to its makers. Russia, France and the United States lag further behind in the competition.
U.S. experts familiar with the Chinese undersea program say it is unusual in that Beijing has little experience in the daunting field. As a result, China is moving cautiously. Jiaolong's sea trials began quietly last year and are to continue until 2012, its dives going deeper in increments.
"They're being very cautious," Walsh said. "They respect what they don't know and are working hard to learn."
In an interview, Walsh said that the Chinese were especially interested in avoiding the embarrassment of a disaster that ends with the aquanauts' entrapment or death. "If I'm the new kid on the block," he said, "I'm going to make sure that I've got bragging rights."
China's splash in the arcane world of submersibles comes after years of singling out major industries and technologies for rapid development. China is also rushing to make supercomputers and jumbo jets.